KR101620806B1 - Nonpolar liquid and solid phase change ink compositions comprising nanosized particles of benzimidazolone pigments - Google Patents

Abstract

The ink composition of the present invention comprises a nonpolar carrier and a nanoscale pigment particle composition wherein the nanoscale pigment particle composition comprises a sterically bulky stabilizer compound non-covalently associated with a benzimidazolone pigment and a benzimidazolone pigment Wherein said sterically bulky stabilizer compound comprises a substituted pyridine derivative; The presence of bound stabilizers limits the degree of particle growth and aggregation to provide nanoscale-sized pigment particles.
Nonpolar liquid and solid phase
The presence of the associated stabilizer limits the degree of particle growth and aggregation to provide nanoscale-sized pigment particles

Description

TECHNICAL FIELD [0001] The present invention relates to a non-polar liquid and solid phase change ink composition comprising nano-sized benzimidazolone pigment particles. BACKGROUND OF THE INVENTION < RTI ID = 0.0 >

The present invention relates to a non-polar and phase-change (or solid) ink composition comprising nanoscale benzimidazolone pigment particles and a process for their preparation.

Pigments for ink-jet inks have a large particle size and a broad particle size distribution, and this combination can cause problems with reliable injection of ink. Pigments are large micrometer-sized aggregates of crystals, and these aggregates often have a broad aggregate size distribution. The color characteristics of the pigments can vary greatly depending on the aggregate size and the crystal morphology. Thus, an ideal colorant widely applicable to inks and toners has the best properties of both dyes and pigments: 1) excellent color characteristics (wide color gamut, luminance, hue, vivid color); 2) color stability and durability (stable colorants in heat, light, chemicals and air); 3) minimal or no color transfer; 4) processable colorants (easy to disperse and stabilize within the matrix); And 5) a colorant having an inexpensive material cost. There remains an additional need for the use of these nanoscale pigment particles in non-polar phase change (solid) ink compositions that enable reliable ink jetting performance and can provide high quality and robust images. There remains a further need for a method of making and using such a phase change ink composition containing nanoscale pigment particles as the colorant material. The present nanoscale pigment particles are also useful in paints, coatings, electrophotographic toners and other uses, such as colored plastics and resins, optoelectronic imaging components and optical color filters, photographic elements and cosmetics .

An aspect of the present invention provides an ink composition comprising nanoscale benzimidazolone pigment particles, for example, a nonpolar liquid or solid phase change ink composition. Nanoscale pigment particle compositions generally include organic benzimidazolone pigments having one or more functional moieties that associate nonfunctional with a functional group from a sterically bulky stabilizer compound, Such sterically bulky stabilizer compounds include substituted pyridine derivatives. The presence of aggregated sterically bulky stabilizers limits the degree of particle growth and aggregation to provide nanoscale particles. In particular, substituted pyridine derivatives are capable of intermolecular and intramolecular hydrogen bonding to limit particle growth and aggregation.

The benzimidazolone pigments include substituted aromatic amines as diazonium salt precursors (or diazo components) and azo-benzimidazolone classes generally derived from coupling agents containing benzimidazolone functional moieties . The azo-benzimidazolone pigments provide hues ranging from yellow to red to reddish, depending mainly on the chemical composition of the coupling component.

The structure of the azo-benzimidazolone pigment employs more than one tautomeric form due to the presence of the N atom of the azo group and the intramolecular hydrogen bond between the H atom of the adjacent heteroatom substituent on the coupling component group can do.

The azo-benzimidazolone pigments can form a one-dimensional extended network due to strong intermolecular hydrogen bonding. Evidence has been found in the X-ray diffraction pattern of these pigments that large intermolecular spacings in the X-ray diffraction pattern cause the pairs of pigment molecules to strongly associate with each other via intermolecular H bonds, resulting in a one- dimensional band or ribbon microstructure assembly ). ≪ / RTI >

The presence of these intracellular and intermolecular hydrogen bonds in these reinforcing molecules leads to improved performance characteristics of the azo-benzimidazolone pigments, such as high thermal stability, high light fastness, high color-migration resistance, And evidence of high solvent fastness. The benzimidazolone functional moieties in these pigments are key structural elements that enable the formation of intermolecular hydrogen bonds and provide improved robustness. This residue readily participates in single point and double point hydrogen bonding, and another compound having the same or different functional moiety can be attached to the azo-benzimidazolone pigment in noncovalent association, for example, via intermolecular hydrogen bonding And thus will have a high binding affinity for these pigments. These are groups of compounds termed "stabilizers " which reduce the surface tension of the pigment particles and offset the attractive forces between the two or more pigment particles or structures, whereby the chemical and physical structure of the pigment . These compounds have "pigment-affinity" functional moieties and may also contain one or more hydrophobic groups, such as long alkyl hydrocarbon groups, or alkyl- Wherein the alkyl group may be a linear, cyclic or branched structure and may have a total of at least 6 carbons. The presence of additional hydrophobic groups within such stabilizers can provide several functions: (1) commercializing the pigment for better dispersibility in the targeted vehicle or matrix, and (2) Thereby providing a three-dimensionally bulky layer thereby preventing or limiting access to uncontrolled crystal aggregates and other pigment particles or molecules that ultimately lead to grain growth. A compound having both pigment-friendly functional moieties that associate non-covalently with the pigment, as well as one or more sterically bulky hydrocarbon groups that provide surface barriers to other pigment particles, is referred to as a "steric stabilizer" (Such as latex particles in paints, metal oxide nanoparticles in anti-scratch coatings) that require ordinary pigment and stabilization.

The benzimidazolone pigment / precursor may form one or more hydrogen bonds per benzimidazolone unit or molecule with the selected stabilizing compound. The benzimidazolone pigment / precursor may form from 1 to 4 or more hydrogen bonds per benzimidazolone with the selected stabilizer compound.

The stabilizer has the function of limiting the degree of aggregation of primary pigment particles in order to limit the self-assembly of the colorant molecules during pigment synthesis and / or to predominantly produce nanoscale pigment particles. The stabilizer has a hydrocarbon moiety that provides steric bulk sufficient to enable the function of the stabilizer to control the pigment particle size. The hydrocarbon moieties are predominantly aliphatic, but in other embodiments may also contain aromatic groups, and the hydrocarbon moieties contain at least 6 or at least 12 or at least 16 carbons, and at most 100 carbons. The hydrocarbon residue may be linear, cyclic or branched and may or may not contain cyclic moieties such as cycloalkyl rings or aromatic rings. The aliphatic bases are two or more carbons and not more than 100 carbon atoms in each branch.

The term "steric bulkiness" is understood to be a relative term based on a comparison of the size of the pigment or pigment precursor with which it is noncovalently associated. The phrase "three-dimensionally bulky nature" means that the hydrocarbon moiety of the stabilizer compound to which hydrogen is bonded to the pigment / precursor surface is a residue of another chemical entity (e.g., a colorant molecule, a primary pigment particle or a small pigment aggregate) facing the pigment / Refers to a situation that occupies a three-dimensional space volume that effectively prevents access or association. The stabilizer may be selected so that its hydrocarbon residue is associated non-covalently with a pigment / pigment precursor by several stabilizer molecules (e.g., by hydrogen bonding, van der Waals forces, aromatic pi-pi interactions, , Wherein these stabilizer molecules act as a surface agent for the primary pigment particles that effectively block the primary pigment particles thereby limiting the growth of the pigment particles and predominating the pigment nanoparticles to provide.

Suitable stabilizing compounds are amphipathic; They are hydrophobic or polar functional groups with heteroatoms available for hydrogen bonding with pigment / pigment precursors, as well as predominantly aliphatic (or fully saturated) with at least 6 to 100 carbons, but some ethylenically unsaturated groups ≪ / RTI > and / or an aryl group.

Substituted pyridine derivatives, particularly mono- and disubstituted pyridine derivatives, may also be used. Substituted pyridine derivatives include compounds of formula (5): < RTI ID = 0.0 >

In various embodiments, the pyridine derivatives of formula 5 have substituents R ₁ to R ₅ , which may be the same or different. Suitable examples of functional groups for R ₁ to R ₅ in formula (5) are H, an amide group (-NH- (C = O) -R ') and (- (C = O) -NH-R'); Amine group (-NH-R '); Urea group (-NH- (C = O) -NH-R '); Carbamate or urethane groups (-NH- (C = O) -O-R ') and (O- (C = O) -NH-R'); Ester group (- (C = O) -O-R ') or (-O- (C = O) -R'); Branched or linear alkyleneoxy chains such as oligo-or poly- [ethylene glycol], and the like; And an alkoxy group (-OR '), wherein the group R' in all the various functional groups is predominantly a linear or branched alkyl or cycloaliphatic group, which contains a heteroatom such as O, S or N ").≪ / RTI >

In certain embodiments, exemplary substituted pyridine derivatives include compounds of formula 6: < RTI ID = 0.0 >

In the above formula (6)

X each independently represents -N (H) - or -O-,

R ₁ and R ₂ independently represent a linear or branched alkyl or cycloaliphatic group, which may contain heteroatoms, such as O, S or N, in the alkyl group.

R ₁ And specific non-limiting examples of R < ₂ > groups include:

In the above formulas,

m and n independently represent integers from 0 to about 30;

These disubstituted pyridine derivatives are preferably amphipathic compounds. That is, these compounds include pigment-friendly groups that are capable of H-bonding to the benzimidazolone functional moiety of the pigment, such as 2,6-pyridinedicarboxylate esters or dicarboxamide residues. This H-bond can potentially interfere with the intermolecular H-bond network of the pigment, thereby preventing or limiting particle growth and aggregation. The compounds also include bulky aliphatic groups that provide a steric barrier layer on the pigment surface, which also helps limit or disperse the access of other colorant molecules to form larger crystals.

In the above formula (5), groups R ₁ to R ₅ May also have a bifunctional structure that bridges two or more pyridyl groups, for example, as in the following formula: < RTI ID = 0.0 >

!!

!!

Examples of suitable difunctional groups R _y and R _z are - (CH ₂ ) _n ; -X- (CH ₂ ) _n X; _{- [(XCH 2 CH 2)} n] X-; - [(C = O) - (CH 2) n - (C = O)] -; -X - [(C = O) - (CH 2) n - (C = O)] - X-; -X - [(C = O) -X- (CH 2) n -X- (C = O)] - X-; - [(C═O) -X- (CH ₂ ) _n -X- (C═O)] -, wherein X is O, S or NH and the integer n is 1 to 500 ; Also, a large branched alkylation group for the group R < _{z &} gt ;, for example,

(Wherein X, X ₁ and X ₂ are defined as O, S or NH, and X ₁ and X ₂ may or may not be the same).

Specific examples of substituted pyridine derivatives include, without limitation, compounds of the following Tables 1 and 2:

The pyridine derivatives substituted in the 2 and / or 6 positions (in Table 1, where R ₁ and R _5, respectively) are prepared from commercially available materials using known chemical transformations. By way of example, when both the 2 and 6 positions are carboxylated functional groups such as [pyridyl] - (C = O) -NHR, which is an amide, or [pyridyl] - (C = O) for the synthesis of 2,6-disubstituted pyridine, a catalytic amount of from step 1 in a suitable organic solvent (eg, tetrahydrofuran (THF) or dichloromethane _{(CH 2 Cl 2)) N} , N - dimethylformamide (DMF In the presence of a suitable reagent such as, for example, oxalyl chloride or thionyl chloride, to the corresponding acyl chloride. In a second step, the acid chloride group is then reacted with a suitably sterically bulky primary or secondary alkyl amine or alcohol in the presence of an acid-trapping, non-nucleophilic base, such as triethylamine.

Reverse 2-monoamido or diamidopyridine derivatives are also prepared from commercially available materials using known chemical transformations. By way of example, 2,6-diaminopyridine may be reacted with one or more equivalents of the appropriate alkanoic acid chloride in the presence of a non-nucleophilic base such as, for example, triethylamine, so that both the 2 and 6 positions are reversed carboxylamides, For example, to produce the desired 2,6-diamidopyridine compound of [pyridyl] -NH- (C = O) -R. When the alkanoic acid chloride is not available, it is reacted with a catalytic amount of N, N -dimethylformamide (DMF) in a suitable organic solvent (i.e., tetrahydrofuran (THF) or dichloromethane (CH ₂ Cl ₂ ) Is conveniently prepared by conversion of the corresponding alkane carboxylic acid using a suitable halogenating agent such as, for example, oxalyl chloride or thionyl chloride.

Any of the above stabilizers and combinations thereof may be used in the preparation of nanoscale pigment particles in amounts ranging from 0.5% to 50% by weight, for example from 1% to 25% by weight.

The "average" pigment particle size (expressed in d ₅₀ ) for "nanoscopic", "nanoscopic" or "nano-sized" pigment particles is less than 150 nm, or from 1 nm to 120 nm, Or 10 nm to 100 nm.

Nanoparticles of azo-benzimidazolone pigments are generally synthesized in one or more process steps. The pigment nanoparticles are produced directly in the reaction medium during synthesis, but it is possible to tailor the surface chemistry to the intended use of such pigment nanoparticles by any post-synthesis purification. The bulk azo-benzimidazolone pigment is subjected to a diazotization and coupling reaction in the first step and then subjected to a second process step by a pigment re-precipitation method in which a crude bulk pigment is molecularly dissolved using a good solvent It can be synthesized by converting the pigment solids into nanoparticle form, followed by pigment precipitation by controlled addition of non-solvent. Direct synthesis of azo-benzimidazolone pigment nanoparticles by diazotization and coupling processes can be used and is preferred. These processes are shown generally in Scheme 1 and Scheme 2 below:

[Reaction Scheme 1]

[ Reaction Scheme 2]

A process for preparing nanoscale particles of an azo-benzimidazolone pigment (referred to simply as a benzimidazolone pigment in this specification) such as those exemplified in the general reaction in Schemes 1 and 2 involves at least one reaction Is a direct synthesis process. Diazotization is a key reaction step in which a suitably substituted aromatic amine or aniline precursor is converted, directly or indirectly, to its corresponding diazonium salt. A typical reaction procedure is to add an aqueous solution of the precursor to an effective diazotizing agent, such as nitrite HNO ₂ , which is produced in situ by reaction of sodium nitrite with a dilute acid solution, such as hydrochloric acid, (NSA), which may be prepared by mixing sodium nitrite in commercial or concentrated sulfuric acid. The diazotization reaction is carried out in an acidic aqueous solution and at low temperature in order to keep the diazonium salt thermally stable, but it can be carried out at room temperature. This reaction leads to the formation of the diazonium salt, which is dissolved in the medium or finely suspended in the medium as solid particles.

The second solution or solid suspension is prepared by dissolving or suspending the benzimidazolone coupling component (most commonly the CC1 or CC2 structure shown above) in an aqueous medium, usually an alkaline solution to aid dissolution, Or base to form the benzimidazolone coupling component into a buffered acidic aqueous solution or buffered fine suspension necessary for reaction with the diazonium salt solution. Suitable acids, bases and buffers include sodium hydroxide, potassium hydroxide, acetic acid, and sodium acetate. The solution or fine suspension of the coupling agent may be mixed with other liquids such as an organic solvent (e.g., iso-propanol, tetrahydrofuran, methanol, N -methyl-2-pyrrolidone, N, N -dimethylacetamide, dimethylsulfoxide, and the like). The second solution further contains any of the surface active agents previously described and the sterically bulky stabilizer compound. This second solution is filled into a larger vessel to perform the final reaction step, wherein the final reaction step is carried out at an ambient temperature of from about 10 [deg.] C to about 75 [ At other suitable temperatures, including controlled addition of a diazonium salt solution, thereby yielding a pigment solids as a suspended precipitate in an aqueous slurry. There are several chemical and physical processing parameters that will affect the quality and characteristics of the pigment particles-for example, the average crystallite size, particle shape and particle distribution-these processing parameters include the relative chemistry of the starting diazo and coupling components as reactants The order and rate of addition of reactants, the type and relative amount (loading) of any surfactant and / or steric stabilizer compound used in the synthesis, the relative concentration of species in the liquid medium, the pH of the liquid medium, the coupling The temperature during the reaction, the stirring rate, the post-synthesis step, for example, the heating to increase the tinctorial strength, and also the recovery and drying of the final particles.

In the preparation of azo-benzimidazolone pigments containing a single azo group, the starting diazo and coupling components are provided in an approximate stoichiometric (or 1: 1 mole) ratio. The coupling component may have a limited solubility in the coupling medium while the diazo component may be generally soluble and may contain from about 0.01 to about 0.25 molar equivalents of excess diazo component relative to the number of moles of coupling component, It is advantageous to use very small excess diazo components, ranging from 0.01 to about 0.10 molar equivalents. By having a slight molar excess of the diazo component, all insoluble coupling components are completely converted to the pigment product. The excess diazo component will then be removed by washing the final product. If an excess of insoluble coupling component is used, any unreacted coupling component will remain in the final product mixture, which is difficult to remove by washing and may affect the properties of the nanoscale pigment.

The reaction conditions can affect the quality and properties of the pigment particles. For the diazotization reaction, the liquid medium is maintained such that the concentration of the diazo component or diazonium salt reactant does not exceed about 0.1 M to about 1.0 M, or about 0.2 M to about 0.80 M, or about 0.30 M to about 0.60 M . Diazotization reagent - preferably, the amount of water soluble and acid-miscible reagent, such as sodium nitrite or nitrosyl sulfate, is approximately stoichiometric (or 1: 1) relative to the molar amount of diazo component used Molar ratio), but with excess diazotization reagent in the range of about 0.005 to about 0.20 molar equivalents relative to the number of moles of diazo component precursor, very little excess diazotization reagent can also be used. The type of acid that can be used may include any suitable mineral acid, such as hydrochloric acid and sulfuric acid, as well as organic acids such as acetic acid and propionic acid, or various combinations. In the case of the diazotization reaction used for the synthesis of the colorant, the acid reactant is delivered as an aqueous solution to solubilize the diazonium salt obtained by forming the reactive nitrosylation species and the reaction. The concentration of the acid reactant is used in excess with respect to the number of moles of the diazo precursor (the limiting reagent), which is in the range of from about 1.5 to about 5.0 or from about 2.0 to about 4.0 in excess of the molar equivalent of acid to moles of diazo precursor Lt; / RTI >

The diazotization reaction is carried out at a low temperature to make the resulting diazonium salt product thermodynamically stable. The diazotization reaction is carried out at a temperature of from -10 ° C to about 5 ° C, or from about -5 ° C to about 3 ° C, or from about -1 ° C to about 2 ° C. The nitroxylation reagent is added to the aqueous solution to provide the total diatomic salt concentration as described above and the rate at which this aqueous solution of the nitroxylation reagent is slowly added can vary depending on the scale of the reaction. This rate of addition is controlled by maintaining the internal temperature throughout the course of the diazotization reaction between -10 ° C and 5 ° C, or between about -1 ° C and about 2 ° C. After complete addition of the nitrosylating reagent, the diazotization reaction mixture can be stirred for 0.25 hours to about 2 hours.

In addition, many of the disclosed sterically bulkier stabilizing compounds also have poor solubility characteristics of the coupling components and / or pigments because they have polar hydrogen-bonding groups and also long alkyl chains that resist solubilization in an aqueous medium Because it is an amphibolite structure. For a successful coupling reaction step, it is necessary to ensure effective wetting and mixing of the coupling component and the sterically bulky stabilizer before addition of the diazonium salt solution. By having good miscibility and wettability in the coupling component mixture prior to reaction with the diazonium salt, the pre-formation of hydrogen-bonding interactions between the steric stabilizer and the coupling agent will be dissolved, The particle size and morphology of the pigment nanoparticles can be favorably influenced.

The coupling component mixture of various embodiments consists of a coupling component suitable for the synthesis of a benzimidazolone pigment, a sterically bulky stabilizing compound, an alkaline base component, at least one acid buffer component, and optional water-miscible organic solvent do. The amount of coupling component used is stoichiometric (or 1: 1 molar ratio) relative to the diazo component, as described above. However, the coupling component may have a limited solubility in the coupling medium, while the diazo component may dissolve and an excess of the diazo component relative to the moles of coupling component may be present in the coupling medium in an amount of from about 0.01 to about 0.25 molar equivalents, 0.01 to about 0.10 molar equivalents. By having a slight molar excess, all insoluble coupling components are completely converted to the pigment product. The alkaline base allows the coupling component to dissolve in an aqueous solution, which can be dissolved in an aqueous solution from an inorganic base, such as sodium hydroxide or potassium hydroxide, or from an organic, non-nucleophilic base such as triethylamine, triethanolamine, diethylaminoethanol , Dytek series of amines, DABCO (1,8-diazobicyclo [2.2.2] octane), and the like. Excess alkaline bases may be used wherein the molar excess of the base relative to the number of moles of coupling component is in the range of from about 2.0 to about 10.0, or from about 3.0 to about 8.0. The acid neutralizes the base component and the coupling component, causing fine reprecipitation of the coupling component in the buffered aqueous medium. Common inorganic and organic acids such as hydrochloric acid or acetic acid may be used and may be used in a molar ratio of 1: 1 based on the total amount of alkaline base components used to prepare the coupling component mixture, providing a weak acid buffering medium .

The steric stabilizer compound may be introduced directly into the coupling mixture, either in the form of a solid or liquid, or as a solution in an organic solvent. The amount of steric stabilizer compound added may vary as long as the steric stabilizer is made in dispersed, emulsified or soluble form in an organic solvent and may be present in an amount of from about 0.01 weight percent (based on the final yield) of the benzimidazolone pigment % To about 50 wt%, or from about 0.5 wt% to about 25 wt%, or from about 5 wt% to about 10 wt%. Any water-miscible organic solvent may be used, provided that it does not react with the diazonium salt reagent or any remaining nitrosylation species, examples of which include aliphatic alcohols such as methanol, ethanol, isopropanol, n- Butanol, isobutanol, sec-butanol, hexanol, cyclohexanol, dimethylsulfoxide, ethylmethylsulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidinone, tetra Alkylene glycols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, Dowanol (R) and mono- or di-alkyl ethers thereof, and the like. Particularly suitable solvents include aliphatic alcohols such as methanol, ethanol, isopropanol and n-butanol, dimethyl sulfoxide and tetrahydrofuran, or combinations thereof. The amount of any organic solvent may range from about 0 to about 50 volume percent, and preferably from about 2 to about 20 volume percent, based on the total liquid volume of the coupling component mixture.

In order to promote dispersion, emulsification or solubilization of the stabilizing compound, heating, or high-shear mixing, may be used, also in the presence of any organic solvent. In certain embodiments, it is also advantageous to incorporate the stabilizing agent into the aqueous coupling medium at a temperature in the range of from 10 to 100 DEG C in order to achieve good dispersion. The stabilizing agent may also be introduced into an aqueous coupling medium at a pH in the range of about 3-12. The stabilizing agent may be added to the coupling mixture at a pH ranging from 2 to 9 or from 4 to 7. Stabilizers may be added to the coupling mixture at any suitable rate, so long as proper mixing and dispersion is achieved.

The order of addition of the reactants is 1) direct addition of a steric stabilizer (in neat or organic solvent) into the alkaline solution of the coupling component, followed by the addition of the acid component to remove the coupling component in the buffered acidic medium Causing fine reprecipitation; Or 2) separately and sequentially adding an alkaline solution of the coupling component and a steric stabilizer (in a pure state or in an organic solvent) to the aqueous solution of the acid component prepared, in the presence of the steric stabilizer compound under acidic conditions, It may be causing a fine reprecipitation. Both of these methods allow the coupling component to be made as a fine particle suspension by a non-covalently associated steric stabilizer compound.

In the case of the final coupling reaction, the order and rate of addition of these core reactants in the presence of the steric stabilizer can affect the physical and performance characteristics of the final benzimidazolone pigment particle. In various embodiments, the "continuous addition" method used includes steps that are commonly practiced in the manufacture of industrial pigments in which two pigment precursors (diazo and coupling components) are dispersed or emulsified in a steric stabilizer Are continuously added to the final reaction mixture already containing the compound at different times. For example, in the synthesis of Pigment Yellow 151 nanoparticles according to this sequential process of reactant addition using the steric stabilizer compound number 23 (where m = 11 and n = 9) of Table 1, According to the SEM / STEM image, a short film having a length: width aspect ratio in the range of about 2 to about 5 and an average particle size measured by dynamic light scattering of about 50 nm to about 200 nm, more typically about 75 nm to about 150 nm The formation was observed to be dominant particles and aggregates.

The internal temperature of the coupling reaction mixture may range from about 10 캜 to about 60 캜, or from about 15 캜 to about 30 캜, to produce an aqueous slurry of the benzimidazolone pigment nanoparticles. An internal temperature of greater than 30 DEG C may undesirably increase the final pigment particle size. The benefits of heating chemical reactions include faster reaction times and the expression of end products such as the color of benzimidazolone pigments, but heating is known to promote aggregation and coarsening of particles, I do not.

An alternative to increasing the internal temperature to accelerate the reaction is to increase the stirring speed. As the pigment is formed, the mixture becomes very dense, requiring strong mechanical stirring to achieve sufficient mixing. It may be possible to lower the viscosity of the slurry by adding a very small amount of surface active agent, for example, a few drops of 2-ethylhexanol, which also provides a beneficial defoaming effect, especially on a larger scale of the reaction can do. The shear force exerted during vigorous stirring of the reaction mixture can provide a synergistic gain in combination with the gain of the surfactant in viscosity and control of bubble formation and also in the reduction of the size and size distribution of the pigment nanoparticles.

The slurry of pigment nanoparticles is not further processed or processed, and is instead immediately separated by a vacuum filtration or centrifugation process. In contrast to known processes which require boiling of the product in concentrated acetic acid to aid color development, such subsequent treatments are not required if a sterically bulky stabilizer component is used. The pigment solids can be thoroughly washed with deionized water to remove excess salts or additives - they are not firmly associated or bonded to the pigment particle surface. The pigment solids are dried by freeze-drying under high vacuum or by vacuum-oven drying at a temperature of about 25-50 C to prevent primary nanoparticles from fusing during heat-induced bulk drying. The pigment obtained is a nano-scale primary particle and a loosely-packed pigment which, when imaged by a TEM (transmission electron microscope), exhibit rod-shaped nanoparticles having a length of from about 50 nm to about 150 nm and predominantly from about 75 nm to about 125 nm It is predominantly made up of nanoscale grain aggregates that are bulky and of high quality. These values were in the range of about 80 nm to about 200 nm or about 100 nm to about 150 nm when measured for average particle size, Z-average, or d ₅₀ by dynamic light scattering technique as colloidal dispersion in n-butanol. Wherein the average particle size, d _50, or Z-average is measured by dynamic light scattering, which measures the intensity of incident light scattered from moving particles, thereby gyrating and moving through the Brownian motion in the liquid dispersion It should be noted that this is an optical technique for measuring the hydrodynamic diameter of non-spherical pigment particles.

The shape of the nanoscale benzimidazolone pigment particles using the above method is rod-shaped, but may be one or more of several other morphologies, and the aspect ratio of the nanoscale pigment particles may be 1: 1 to about 10: 1, or 1 : 1 to 5: 1.

Pigment particles of benzimidazolone pigments such as Pigment Yellow 151 and Pigment Red 175 having smaller particle sizes can also be used in the absence of the use of sterically bulky stabilizers and on the surface Such a pigment product will not predominantly exhibit nanoscale particles, although it may be prepared by the above method using only the active agent (e.g., using only rosin-type surface agents) Nor will it exhibit a regular morphology. In the absence of the use of sterically bulky stabilizing compounds, the methods described above generally provide a broad distribution of particles having an average particle diameter of greater than 150 to 1000 nm and a large (length: width) aspect ratio of greater than about 5: 1 Thereby producing an elongated bar-shaped grain aggregate. Such particles are very difficult to wet and / or disperse into the matrix for coating applications and will generally provide poor color characteristics. Using the synthesis methods described above, the combined use of a suitable sterically bulky stabilizer compound and, optionally, a small amount of a suitable surface active agent, such as a rosin-type surfactant or alcohol ethoxylate, A particle size distribution, and a small pigment particle having a low aspect ratio of less than about 5: 1.

Advantages of this method include the intended end-use application of the benzimidazolone pigment, such as toner and ink, and the ability to adjust the particle size and composition for coating, which may include phase change, gel-based and radiation- Curable inks, solid and non-polar liquid inks, solvent-based inks and aqueous inks and ink dispersions. For end-use applications in piezoelectric inkjet printing, nanoscale particles are advantageous to ensure reliable inkjet printing and to prevent blockage of the jet caused by pigment particle aggregation. In addition, nanoscale pigment particles are advantageous in providing improved color characteristics in printed images.

The formed nanoscale pigment particle composition can be used, for example, in a variety of ink compositions, including, for example, liquid (aqueous or nonaqueous) ink vehicles-such as those used in conventional pens, , Solid or phase change ink compositions, and the like. For example, the colored nanoparticles may be used in solid and nonpolar phase change inks, solvent-based liquid inks or radiation-curable, e.g., UV-curable liquid inks having a melting temperature of about 60 to about 130 & May be formulated into various ink vehicles, including ink.

The nonpolar liquid and solid phase change ink compositions may comprise a carrier, a colorant and one or more optional additives such as a solvent, a wax, an antioxidant, a tackifier, a slip aid, a curable component, And / or polymers, gelling agents, dispersants, initiators, sensitizers, wetting agents, biocides, preservatives and the like. The formed nanoscale benzimidazolone pigment particles can be used in such inks as colorants or as nano-fillers for improved mechanical robustness.

The nonpolar liquid and solid phase change ink compositions contain one or more coloring agents. Any desired or effective colorant may be used in these ink compositions, including pigments, dyes, mixtures of pigments and dyes, mixtures of pigments, mixtures of dyes, and the like. The colorant used in the ink composition consists entirely of the nanoscale benzimidazolone pigment particles formed. However, nanoscale benzimidazolone pigment particles may be used in conjunction with other colorant materials, wherein the nanoscale benzimidazolone pigment particles comprise substantially the majority of the colorant material (e.g., about 90 wt% or about 95 wt% (E. G., Greater than or equal to 50% by weight) of the colorant material, or they may form a minor portion (e. G., Less than about 50% can do. The two main advantages of using nano pigments over larger size commercial pigments are their reliable injection of ink formulations (printhead reliability) and the improved color performance of the nano pigments - which allows the reduction of pigment loading in the ink composition To ensure that the Nanoscale benzimidazolone pigment particles may also be included in the ink composition in any other various amounts to function as a colorant and / or function as a nano-filler in order to enhance other properties such as image fidelity.

The non-polar ink composition also includes a carrier material, which may be liquid or solid, or a mixture of two or more carrier materials. In the case of liquid ink compositions, such carriers for inks may be selected from the group consisting of aprotic and nonpolar liquids such as acetone, acetonitrile, methyl ethyl ketone and methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, iso Simple ketones and esters such as propyl acetate, methoxypropyl acetate, N -methylpyrrolidinone, sulfolane, N, N -dimethylformamide, N, N -dimethylacetamide and the like; Mono-alkyl ethers of tetrahydrofuran, dimethoxyethane, tetrahydrofurfuryl alcohol, sol-ketal, diethylene or dipropylene glycol, such as diethylene glycol monomethyl ether, dipropylene glycol methyl Ethers such as ether, DOWANOL® and the like; Aromatic hydrocarbons such as toluene; o-, p- and m -xylene and mixtures thereof; Mono- and dichlorobenzene; Terpenoid solvents such as limonene, pinene, camphene, parresene and the like; And linear or branched aliphatic hydrocarbons such as hexane, paraffinic hydrocarbons and the like; And mixtures thereof. For example, examples of suitable straight chain and branched chain aliphatic hydrocarbons having from about 1 to about 30 carbon atoms include the ISOPAR (TM) series of hydrocarbons, manufactured by Exxon Corporation, which comprise a narrow isoparaffinic hydrocarbon fraction . Other suitable solvent materials include, for example, the NORPAR (TM) series of liquids, a composition of n -paraffin available from Exxon Corporation, the SOLTROL (TM) series of liquids available from Phillips Petroleum Company, Includes SHELLSOL ™ series.

Other carrier liquids or solvents that can be used to disperse nanoscale-sized pigments with various polymers and other ink components, such solubility of the polymer and resin being ensured are polyunsaturated fatty acids, such as tung oil ), Dry oils consisting of soybean oil, linseed oil, safflower oil, sunflower seed oil, canola oil, poppy seed oil, perilla oil, oiticil oil, hosin oil, various fish oils and suitable mixtures thereof. Other carrier liquids or solvents that may be used include, but are not limited to, non-drying oils such as paraffinic oils, naphthenic oils, isoparaffinic oils, For example, cyclomethicone and dimethicone, diester oil-dialkyl phthalates such as diisobutyl phthalate, dioctyl phthalate and dioctyl adipate, essential oils such as rose oil, and And suitable mixtures thereof.

In the case of a solid non-polar (or phase-change) ink-jet ink composition, the carrier may comprise one or more organic or polymeric compounds. Carriers for such solid ink compositions are typically solid at room temperature (from about 20 [deg.] C to about 25 [deg.] C), but become liquid at the printer operating temperature for injection onto the printing surface. Thus, suitable carrier materials for solid ink compositions include, for example, amides, including diamides, triamides, tetramides, and the like. Suitable triamides are, for example, those disclosed in U.S. Patent Application No. 2004-0261656. Suitable other amides include, for example, fatty amide-monoamides, tetramides, and mixtures thereof, for example, in U.S. Patent Nos. 4,889,560, 4,889,761, 5,194,638, 4,830,671, 6,174,937 No. 5,372,852, 5,597,856 and 6,174,937, and GB 2 238 792, which are incorporated herein by reference. In embodiments in which an amide is used as the carrier material, the triamide is particularly useful because it is believed that the triamide has a more three-dimensional structure compared to other amides, such as, for example, diamides and tetramides.

Other suitable carrier materials that can be used in the solid ink composition include, for example, isocyanate-derived resins and waxes such as urethane isocyanate-derived materials, urea isocyanate-derived materials, urethane / urea isocyanate- Mixtures, and the like.

Further suitable solid ink carrier materials include paraffin, microcrystalline wax, polyethylene wax, ester wax, amide wax, fatty acids, fatty alcohols, fatty amides and other waxy materials, sulfonamide materials, different natural sources Rosin and rosin esters), and many synthetic resins, oligomers, polymers and copolymers such as ethylene / vinyl acetate copolymers, ethylene / acrylic acid copolymers, ethylene / vinyl acetate / acrylic acid copolymers, Copolymers of acrylic acid and polyamide, ionomers, and the like, and mixtures thereof. One or more of these materials may also be used in mixtures with fatty amide materials and / or isocyanate-derived materials.

The ink composition optionally contains a viscosity modifier. Examples of suitable viscosity control agents include aliphatic ketones, such as stearone, and the like. When any viscosity modifier is present, it can be present in any desired or effective amount, for example, from about 0.1 to about 99 weight percent, or from about 1 to about 30 weight percent, or from about 10 to about 15 weight percent of the ink, Can exist.

These nanoscale pigments can be dispersed in various media. Polymeric binders (polymeric dispersants) that aid in the dispersion and coating capabilities of the nanoscale pigments include derivatives of rosin natural products, acrylic polymers, styrenic copolymers, alpha -olefins such as 1-hexadecene, 1-octa Decene, 1-eicosene and 1-triacontene, copolymers of vinylpyridine, vinylimidazole, vinylpyrrolidone copolymer, polyester copolymer, polyamide copolymer and acetal. Other examples of polymeric dispersants include, but are not limited to, poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate), poly (vinyl acetate), poly (acrylic acid), poly (methacrylic acid) Such as poly (N-vinylcarbazole), poly (methyl methacrylate), polyvinylidene difluoride, polyesters such as MOR-ESTER 49000®, polycarbonate polymers such as Lexan® and Merlon® M-39, and poly (2-hydroxyethyl methacrylate), poly (styrene- b -4-vinylpyridine), polyurethane resins, polyetheretherketone, phenol-formaldehyde resins, Pluronic® and Pluronic® R polymers, glycol polymers such as polyethylene glycol polymers and derivatives thereof, polysulfone, polyaryl ether, polyaryl sulfone, and the like. A suitable mixture of two or more polymers may also be used to disperse the nanoscale pigment in the liquid medium.

Many available commercial dispersants, such as those from BYK-Chemie, Efka Additives and Lubrizol, are suitable for dispersing pigments in various liquid media. However, it is also possible, for example, to incorporate a polymeric resin into the pigmented dispersion to help reinforce the collectively and adherently coated film on the coated substrate, where it is applicable that the pigmented dispersion is used to make the coating It is beneficial. For example, when a small resisted droplet is obtained from a continuous ink jet printing or from a droplet on demand ink jet printing onto a substrate, the inclusion of a polymeric resin in the colored dispersion or the ink allows the desired aspect of the image, , Image gloss or rub can be improved.

Other optional additives to the ink include detergents, tackifiers, adhesives, plasticizers, antioxidants, and the like.

In a non-polar liquid or solid ink composition, the carrier may be present in the ink in any desired or effective amount. For example, the carrier may be present in an amount of from about 0.1 to about 99 weight percent, or from about 50 to about 98 weight percent, or from about 75 to about 90 weight percent of the ink.

The nonpolar solid (phase change) ink compositions of the present invention typically have a melting point of greater than about 50 DEG C, or from about 50 DEG C to about 160 DEG C or higher. The solid ink composition has a melting point of from about 70 캜 to about 140 캜 or from about 80 캜 to about 120 캜. The solid ink composition also has a melt viscosity at injection temperatures (e.g., typically from about 75 ° C to about 140 ° C, or from about 80 ° C to about 130 ° C, or from about 100 ° C to about 120 ° C) About 30 centipoise, or about 5 to about 20 centipoise, or about 7 to about 15 centipoise. Since the solid ink hardness tends to decrease as the viscosity decreases, it is preferable that the viscosity is as low as possible in order to secure a reliable injection performance while still maintaining the desired image firmness.

The ink composition may also optionally contain other functional materials, which may vary depending on the type of printhead in which the ink is used and the printing process. For example, ink compositions are typically designed for direct printing mode on substrates or for use in indirect or offset printing transfer systems.

The ink composition may be prepared by any desired or suitable method. The preparation of a colored nonpolar solid (phase change) ink composition may include part or all of the nonpolar solid ink component in the ink composition during operation of the pigment dispersion. It may also include the dispersion of pigments at various pigment concentrations at various temperatures by various input energies. The pigments can be processed with or without the use of one or more dispersants and are dispersed by various means.

The pigments can be processed using any suitable grinding media in any suitable dispersing equipment, with or without the use of any synergist, with or without the use of one or more dispersing agents. The nonpolar solid phase change ink composition may be prepared by combining some or all of the components and heating the mixture to a temperature above its melting point, for example from about 70 [deg.] C to about 120 [deg.] C, until a substantially homogeneous, ≪ / RTI > If the pigment is the selected colorant, the molten mixture may be pulverized in an attritor or ball mill apparatus to achieve a dispersion in the ink vehicle of the pigment.

Example

Comparative Example 1: Synthesis of Pigment Yellow 151 (no steric stabilizer used, no surfactant used)

An anthranilic acid (6.0 g, available from Sigma-Aldrich, Milwaukee, Wis.), Deionized water (80 mL) and 5 M aqueous HCl solution (20 mL) is charged to a 250 mL round bottom flask. The mixture was stirred at room temperature until all solids dissolved and then cooled to 0 < 0 > C. A solution of sodium nitrite (3.2 g) is dissolved in deionized water (8 mL) and then added dropwise to a solution of anthranilic acid at a rate such that the internal temperature range in the mixture is maintained at 0-5 < 0 > C. Once diazotization is complete, the solution is stirred for an additional 0.5 h. Prior to the coupling reaction, excess nitrite ions are ground using an aliquot of urea aqueous solution. Deionized water (100 mL) and sodium hydroxide (5.5 g) were charged into a 500 mL vessel and dissolved by stirring and then added with 10.5 g of TCI America (Portland, Oregon, USA) Is added into this solution with vigorous stirring until all solids have dissolved to produce a second mixture for the coupling component. Next, a separate solution containing glacial acetic acid (15 mL), 5M NaOH solution (30 mL) and deionized water (200 mL) was added dropwise with vigorous stirring into the alkaline solution of the coupling component, Precipitated as a white suspension, and the mixture is slightly acidic. For the coupling reaction, the cooled diazotization mixture is slowly added dropwise to a suspension of coupling components with vigorous stirring to produce a reddish yellow slurry of the pigment. The slurry is stirred at room temperature for an additional 2 hours, after which time the pigment is separated by vacuum-filtration, washed with several volumes of deionized water (3x250 mL), and freeze-dried. The reddish-yellow granules of the pigment are obtained and the TEM image shows a large aggregate of the rod-shaped particles having a high aspect ratio, wherein the particle diameter is in the range of 200 to 500 nm.

Example 1: Synthesis of substituted pyridine steric stabilizer No. 20 of Table 1

1.02 g (6.09 mmol) of 2,6-pyridinedicarboxylate (Sigma-Aldrich, Milwaukee, WI) and 20 mL of anhydrous tetrahydrofuran (THF) are charged to a 100 mL round bottom flask. The suspension is stirred under an inert atmosphere. To this suspension was added dropwise 2.2 mL (0.0252 mol) of oxalyl chloride (Sigma-Aldrich, Milwaukee, WI) followed by dropwise addition of 3 drops of N, N -dimethylformamide (DMF) as catalyst. After 10 minutes, all solids are completely dissolved and stirring at room temperature is continued for an additional hour. The solvent is then removed by rotary evaporation and the oily residue of the diacid chloride product is dried under vacuum.

4.10 g (0.0115 mol) of PA-24 primary amine (purchased from Tomah products, an affiliate of Air Products Ltd.) and 40 mL of anhydrous THF are charged into a 250 mL round bottom flask. The solution is purged with an inert gas free of oxygen and then cooled to 0 < 0 > C. The cooled solution of 2,6-pyridinedicarboxylic acid dichloride (step I) in 20 mL of anhydrous THF is then slowly added dropwise to the above solution containing the amine. Triethylamine (2.5 mL, 0.0179 mol) was added and the reaction was stirred while warming slowly to room temperature. After the reaction is complete, 10 mL of deionized water and 40 mL of ethyl acetate are added to the mixture and the bottom aqueous layer is removed. The organic layer is washed with deionized water and separated. The solvent was removed by rotary evaporation and the residual product remaining was dried in vacuo to give a viscous amber oil (4.85 g, 95% yield), which has high purity according to NMR spectroscopic analysis.

Example 2: Synthesis of substituted pyridine steric stabilizer No. 23 of Table 1

To a 100 mL round bottom flask is charged 1.04 g (0.00623 mmol) of 2,6-pyridinedicarboxylate (Sigma-Aldrich, Milwaukee, WI) and 20 mL of anhydrous tetrahydrofuran (THF). The suspension is stirred under an inert atmosphere. To this suspension was added dropwise 2.2 mL (0.0252 mol) of oxalyl chloride (Sigma-Aldrich, Milwaukee, WI) followed by dropwise addition of 3 drops of N, N -dimethylformamide (DMF) as catalyst. After 15 minutes, all solids are completely dissolved and stirring at room temperature is continued for an additional 2 hours. The solvent is then removed by rotary evaporation and the oily residue of the diacid chloride product is dried under vacuum.

A three-necked 100 mL round bottom flask is charged with 2,6-pyridinedicarboxylic acid dichloride (the product of Step I) and 5 mL of anhydrous THF, and the mixture is stirred under an inert atmosphere. ISOFOL 20 (a branched alcohol purchased from Sasol America, Texas, USA) is prepared as a 2.5 M solution in anhydrous THF, and 6 mL of this is slowly added to the above acid chloride solution. The reaction mixture is then heated at reflux for 1.5 hours. The mixture is then cooled to room temperature and quenched with a small amount of deionized water. The organic solvent was removed by rotary evaporation to give the product as a viscous yellow oil (4.54 g, 100%), which has a high purity according to NMR spectroscopic analysis.

Example 3: Synthesis of Pigment Yellow 151 nanoparticles using substituted pyridine steric stabilizer

The same procedure as in Comparative Example 1 was repeated except that 0.72 g (5.25 mmol) of anthranilic acid, 10 mL of deionized water, 2.6 mL of 5M hydrochloric acid and 1 mL of 5.9 M NaNO ₂ (5.93 mmol) . After stirring for 30 minutes, a cold diazonium salt solution is slowly added to the suspension of the coupling component prepared by the following method at room temperature:

1.21 g (5.19 mmol) of 5-acetoacetylamino-benzimidazolone (purchased from TCI America) of the steric stabilizer compound prepared according to Example 1 (0.210 g, 0.249 mmol, or 10% by weight theoretical pigment yield) ), 7.2 mL of aqueous 5M sodium hydroxide, and 76 mL of deionized water. After 10 minutes of rapid mechanical stirring, 2.2 mL of concentrated glacial acetic acid is added to the emulsion to give a fine white suspension of the coupling component (for reaction with the diazonium salt solution).

After stirring for 6 hours, the yellow pigment solids are separated by vacuum filtration through a Supor 0.8 um filter membrane cloth (PALL Corp.). The pigment wet cake was reslurried in deionized water and then separated by further vacuum filtration twice before freeze-drying and then the pigment product was obtained as a pale yellow powder (2.02 g). Electron microscopic analysis (SEM / STEM) of the pigment solids predominantly shows small, elongated primary nanoparticles with a length in the range of 20 to 300 nm, most of which are less than about 100 nm. Dynamic light scattering (DLS) analysis of the colloidal solution of the sample (n-BuOH, 0.01 mg / mL) gave an average effective hydrodynamic diameter ( D _eff ) of 101 nm (PDI = 0.235).

Example 4: Synthesis of Pigment Yellow 151 nanoparticles using a substituted pyridine steric stabilizer

1.79 g (13.1 mmol) of anthranilic acid, 30 mL of deionized water and 6.5 mL of 5M hydrochloric acid are mixed with stirring into a three neck round bottom flask equipped with a thermometer. After cooling the clear solution to <0 ° C, 2.5 mL of cold aqueous 5.7M NaNO ₂ (15.7 mmol) is added at a rate that keeps the internal temperature below 0 ° C. The cold diazo solution is stirred for an additional 30 minutes and then it is slowly added to the suspension of the coupling component prepared by the following method at room temperature:

(0.5 g, 0.686 mmol, 10% by weight of theoretical pigment yield) of the steric stabilizer compound prepared according to Example 2 were added to a solution of 3.05 g (13.1 mmol) of 5-acetoacetylamino-benzimidazolone Of aqueous 5M sodium hydroxide and 200 mL deionized water, and the mixture is emulsified by rapid mechanical stirring. After 10 minutes, 5.5 mL of concentrated glacial acetic acid is added to the emulsion to give a fine white suspension of the coupling component (for reaction with the diazonium salt solution).

After stirring overnight, the yellow pigment solids are separated by vacuum filtration through a Supor 0.45 um filter membrane cloth (PALL Corp.). The pigment wet cake was re-slurried in deionized water and then separated by further vacuum filtration twice and then freeze-dried to give pale yellow powder (4.80 g). Electron microscopic analysis (SEM / STEM) of the pigment solids predominantly shows small, elongated primary nanoparticles with a length in the range of 20 to 200 nm, most of which are less than about 100 nm. Dynamic light scattering (DLS) analysis of a colloidal solution of the sample (n-BuOH, 0.01 mg / mL) gave an average effective hydrodynamic diameter ( D _eff ) of 143 nm (PDI = 0.186).

Ink Example 1: Preparation of Solid Ink Formulation with Pigment Yellow 151 Nanoparticles

An ink was prepared from the PY 151 nanoparticles prepared in Example 3 as a base material. 1800.0 g of 1/8 inch diameter 440C grade 25 steel ball available from Hoover Precision Products, Inc. was filled into the Szegvari 01 attritor available from Union Process. The following components were added together in a 600 mL beaker and melt-mixed at 120 DEG C: 76.7 g of distilled polyethylene wax from Baker Petrolite, 21.2 g of triamide wax (triamide as disclosed in U.S. Patent No. 6,860,930), Crompton Corporation 19.1 g of KE-100 resin commercially available from Arakawa Corporation, 0.3 g of Naugard-445 (antioxidant) available from Crompton Corporation, and 14.37 g of OLOA 11000 available from Chevron Corporation. The resulting solution was transferred quantitatively to an attritor. 6.2 g of PY 151 nanoparticles of Example 3 were added to this attritter vessel. The colored mixture was attracted at 175 RPM for 19 hours overnight, and at this point the resulting ink, which exhibited excellent free-flow behavior, was discharged and separated from the steel ball in its molten state.

Ink Example 2: Filtration and freeze-thaw performance of colored solid ink formulations with PY 151 nanoparticles

The ink prepared as in Example 1 was successfully filtered through a 1 [mu] m filter in a KST-47 device available from Advantec MFS, Inc. As a further stress on the ink, the filtered ink was then frozen and then remelted the following day at 120 DEG C, where it was again successfully filtered through a 1 mu m filter. An aliquot of the ink was transferred to a settling tube, and the ink therein was maintained in an oven at 120 캜 for 7 days. No separation of the ink was observed, indicating that the stabilization of the Pigment Yellow 151 nanoparticles in the ink was maintained. Our efforts to incorporate and disperse commercially available larger sized yellow pigments into non-polar solid ink vehicles have not been successful, and therefore this ink of Ink Example 1 is a proven yellow that can be successfully filtered through a &lt; RTI ID = 0.0 & It should be noted that colored non-polar solid inks are indicated.

Ink Example 3: Preparation of solid ink formulations with Pigment Yellow 151 nanoparticles

An ink was prepared from the PY 151 nanoparticles prepared in Example 2 as a base material. 1800.0 g of 1/8 inch diameter 440C grade 25 steel balls available from Hoover Precision Products, Inc. were filled into the Szegvari 01 attritor available from Union Process. The following ingredients were added together in a 600 mL beaker and melt-mixed at 120 DEG C: 65.8 g of distilled polyethylene wax from Baker Petrolite, 22.3 g of triamide wax (triamide as disclosed in U.S. Patent No. 6,860,930), Crompton Corporation 35.6 g of S-180, 20.1 g of KE-100 resin commercially available from Arakawa Corporation, 0.3 g of Naugard-445 (antioxidant) available from Crompton Corporation, and 11.5 g of Lubrizol 2153 available from Lubrizol Corporation. The resulting solution was transferred quantitatively to an attritor. 9.5 g of the PY 151 nanoparticles prepared in Example 2 were added to the reactor vessel. The colored mixture was attracted at 175 RPM for 19 hours overnight, and at this point the resulting ink, which exhibited excellent free-flow behavior, was discharged and separated from the steel ball in its molten state.

Ink Example 4: Filtration and freezing-thawing performance of solid ink formulations with PY 151 nanoparticles

The ink of Ink Example 3 was then successfully filtered through a 1 [mu] m filter in a KST-47 device available from Advantec MFS, Inc. As a further stress on the ink, the filtered ink was then frozen and then remelted the next day at 120 DEG C, where it was again successfully filtered through a 1 mu m filter. An aliquot of the ink was transferred to a settling tube, and the ink therein was maintained in an oven at 120 캜 for 7 days. No separation of the ink was observed, indicating that the stabilization of the Pigment Yellow 151 nanoparticles in the ink was maintained.

The inks of Ink Example 3 and Ink Example 4 were also successfully sprayed in a Xerox Phaser 8860 solid ink jet printer and the resulting prints were fairly uniform in image quality.

Preparation of nonpolar liquid dispersion

To confirm the dispersibility and thermal stability of the various pigments in the non-polar liquid carrier, it was convenient to use Isopar V, which is an inert and non-polar solvent with low vapor pressure and has a viscosity of about 15 centipoise at 25 ° C, Because it is similar to many piezoelectric inkjet inks.

Comparative Example  2: Nonpolar liquid pigment dispersion

A commercially available dispersion of CI Pigment Yellow 151 was prepared in the following manner. 0.42 g of OLOA 11000 (available from Chevron Oronite Company LLC), 6.48 g of Isopar V (available from Univar Canada Ltd.) was added to a 30 mL bottle and stirred to achieve the dissolution of OLOA 11000. To this homogeneous solution was added 70.0 grams of 1/8 inch diameter 440C grade 25 steel and 0.28 grams of CI Pigment Yellow 151 pigment available from Hoover Precision Products, Inc. (available from Clariant Corporation) mill, and the speed was adjusted to rotate the bottle at about 25 RPM to about 90 RPM for four days. After milling the dispersion for 4 days, 1.5 g of the resulting dispersion was transferred to a 1-dram vial and held in an oven at 120 캜, where the viscosity and thermal stability of the dispersion were qualitatively evaluated. The low viscosity dispersions showed only moderate stability at 120 ° C where a slight sedimentation of some pigment particles from the vehicle after heating at 120 ° C for 6 days was evident and the total sedimentation of the pigment after heating at 120 ° C for 13 days This happened.

Example  5: Nonpolar liquid pigment dispersion

Another dispersion was formed in the same manner as in Comparative Example 2, except that Pigment Yellow 151 prepared in Example 2 was used instead of commercially available CI Pigment Yellow 151 pigment (available from Clariant Corporation) .

Example 6: Nonpolar liquid pigment dispersion

Using another synthetic batch of Pigment Yellow 151 nanoparticles prepared according to Example 2, another dispersion was formed in the same manner as in Example 5. [

Preparation of diluted dispersion for particle size evaluation by dynamic light scattering

It was convenient to dilute the dispersion of Comparative Example 2 and the nonpolar liquid dispersion of Example 5 and Example 6 so that the effect of the pigment concentration was eliminated during particle size evaluation by the dynamic light scattering method. The following methods generally summarize the sample preparation techniques applied to each of the aforementioned dispersions. Four drops of dispersion were added to a clean 30 mL bottle containing a solution of 10 g of 0.1 wt% Oloa 11000 in Isopar V and sonicated for 10 seconds gently. A sufficient fraction of the freshly formed diluted dispersion was transferred to a glass cuvette and placed in a Zetasizer HT particle size analyzer (model number ZEN3600, manufactured by Malvern Instruments Ltd.) and measured 5 times for each of 11 runs Was completed. Periodic sampling of the dispersion in a 1-drum vial during aging in an oven at 120 占 폚 was carried out on this and other Isopar V dispersions to be tested, including those of Examples 5 and 6 of the nonpolar dispersions. The dramatic particle size distribution between the nonpolar dispersion of Comparative Example 2 made with commercially available (larger size) PY 151 pigments and the colored dispersion of Example 5 and Example 6 made with PY 151 nanoparticles of the present invention , It is convenient to compare the polydispersity index (PDI) by the measured Z-average (Z _avg ) diameter and intensity value, both of which are summarized in Table 2.

[Table 2]

The _Zavg results from Table 2 indicate that the dispersion containing commercially available Pigment Yellow 151 pigment (obtained from Clariant Corporation) is a ball-milled dispersion containing PY 151 nanoparticles in the present example, Lt; RTI ID = 0.0 &gt; 2 &lt; / RTI &gt; times larger after milling. The polydispersity index of the various dispersion samples aged at 120 DEG C for 13 days showed that the dispersion containing the PY 151 nano pigment example of the present invention is more stable than the dispersion Comparative Example 2 containing the commercially available PY 151 pigment.

The fineness of the dispersion as exemplified by its ability to wet and de-wet on glass is an indicator of dispersion quality. Poor wetting of fluid-based dispersions is typically seen as having poor film quality on glass substrates, for example, showing distinct graininess and discontinuous phases. Such systems contain at least some of the finely dispersed and / or aggregated and coagulated pigment particles. By contrast, excellent wetting of the fluid-based dispersion on a glass substrate is represented, for example, by having a very high transparent film quality, thus indicating that most of the pigment particles are well dispersed. The dispersion stability over time and temperature can also be qualitatively evaluated and graded by the methods described above. The visual evaluation of the quality of the Isopar V liquid nonpolar dispersions prepared in Comparative Example 2, Dispersion Example 5 and Example 6, which were aged in a glass vial at 120 ° C, was completed and summarized in Table 3.

A small, more thermally stable particle size distribution from the prepared nonpolar liquid dispersion containing the PY 151 nanoparticles of the present invention was compared to a nonpolar liquid dispersion made of commercially available Pigment Yellow 151. The smaller and more thermally stable PY 151 particle size distribution of the present invention makes the nanoscale PY 151 pigment of the present invention much more suitable for use in ink jet printing inks containing piezo ink jet printing inks.

Claims (21)

An ink composition comprising a non-polar carrier and a nanoscale pigment particle composition,
Wherein the nanoscale pigment particle composition comprises a benzimidazolone pigment and a sterically bulky stabilizer compound non-covalently associated with the benzimidazolone pigment,
Wherein the sterically bulky stabilizer compound comprises a substituted pyridine derivative,
The presence of said sterically bulky stabilizer compound associated with said benzimidazolone pigment limits the degree of particle growth and aggregation to provide nanoscale-sized pigment particles. The ink composition of claim 1, wherein the nanoscale pigment particle composition imparts hue to the ink composition. The ink composition of claim 1, wherein the carrier is present in an amount of from 0.1 to 99% by weight of the ink, and wherein the nanoscale pigment particle composition is present in an amount of from 1 to 50% by weight of the ink. The ink composition of claim 1, wherein the carrier comprises a nonpolar liquid that disperses the nanoscale pigment particle composition in the ink composition. The ink composition of claim 1, wherein the carrier comprises at least one non-polar compound that is solid at room temperature but becomes liquid at a printer operating temperature for ejecting the ink composition onto a printing surface. The composition of claim 1, wherein the carrier is selected from the group consisting of amides, isocyanate-derived resins and waxes, paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, amide waxes, fatty acids, fatty alcohols, fatty amides, Polymers and copolymers, and mixtures thereof. The composition of claim 1, wherein the carrier is selected from the group consisting of ketones, esters, ethers and glycol ethers, toluene, xylene, chlorinated benzene, terpenoid solvents, straight or branched chain aliphatic hydrocarbons, Oils, essential oils, and mixtures thereof. The ink composition according to claim 1, wherein the ink composition is a liquid at room temperature. The composition of claim 1, further comprising one or more additives selected from the group consisting of a surfactant, a light stabilizer, a UV absorber, optical brighteners, a thixotropic agent, a dewetting agent, a slip agent, a foaming agent, Wherein the ink composition further comprises at least one additive selected from the group consisting of plasticizers, binders, electrical conductors, fungicides, bactericides, organic and inorganic filler particles, leveling agents, emulsifiers, antistatic agents, dispersants and mixtures thereof. . The ink composition of claim 1, wherein the nanoscale pigment particle composition is present in the ink composition in an amount of at least 50% by weight of the total colorant material in the ink composition. The ink composition of claim 1, further comprising a further colorant compound selected from the group consisting of pigments, dyes, mixtures of pigments and dyes, mixtures of pigments and mixtures of dyes. The ink composition of claim 1, wherein the nanoscale pigment particles have an average particle diameter of less than 150 nm derived from transmission electron microscopy images. The ink composition of claim 1, wherein said sterically bulky stabilizer is associated with a benzimidazolone pigment by non-covalent interaction. The ink composition of claim 1, wherein the sterically bulky stabilizer is a compound of formula (5).
Formula 5

In the above formula (5)
R ₁ to R ₅ may be the same or different and are selected from the group consisting of H, -NH- (C═O) -R ', - (C═O) -NH-R', -NH-R ' (= O) -NH-R ', -NH- (C = O) -O-R', O- (C = O) -NH-R ' - (C = O) -R ', branched or linear alkyleneoxy, or -OR' where R 'is a linear or branched alkyl or cycloaliphatic group which may contain a heteroatom in the alkyl group, . The ink composition according to claim 1, wherein the sterically bulky stabilizer is a compound of the following formula (6).
6

In the above formula (6)
X represents -N (H) - or -O-,
R ₁ and R ₂ independently represent a linear or branched alkyl or cycloaliphatic group, which may contain heteroatoms. 16. The method of claim 15 wherein, R ₁ and R ₂ have the general formula

&Lt; / RTI &gt; The ink composition according to claim 15, wherein R ₁ and R ₂ are the same. The ink composition of claim 1, wherein the sterically bulky stabilizer compound comprises a substituted pyridine derivative selected from the group consisting of the following compounds.

The ink composition according to claim 1, wherein the ink composition can be successfully filtered through a 1 탆 filter before and after treating the ink composition with a cycle of freezing and re-melting at a temperature of more than 100 캜. The ink composition according to claim 1, wherein the ink composition is a solid ink composition and is not separated after heating for 7 days at a temperature of more than 100 캜. The ink composition according to claim 1, wherein the ink composition is a liquid ink composition and is not separated after heating for 7 days at a temperature of more than 100 캜.